Yearly Trends of Antimicrobial Non-susceptibility among Streptococcus pneumoniae Serotypes Causing Infections in Adult Patients in the United States (2009–2015)

BACKGROUND: The implementation of pneumococcal conjugate vaccination (PCV) in children with the 7-valent and 13-valent PCV in 2000 and 2010, respectively, has reduced the incidence of pneumococcal disease, nasopharyngeal carriage and changed the epidemiology of S. pneumoniae serotypes (STs). This study describes the yearly trends in antimicrobial non-susceptibility (NS) rates in pneumococci during 2009–2015. METHODS: 6,197 S. pneumoniae originated from patients (≥18 years old) seen/hospitalized in 105 US sites and recovered primarily (78.3%; 4,852/6,197) from lower respiratory tract specimens. Identification was performed by biochemical algorithms and/or PCR, and susceptibility (S) testing used broth microdilution. MIC interpretation applied CLSI criteria. The cpsB sequence was obtained by PCR or whole genome sequencing for STs determinations. Multiplex PCR and/or Quellung reactions were also performed, as needed. RESULTS: All isolates were highly S to levofloxacin (98.7–99.2%), vancomycin (100.0%), and linezolid (100.0%). PCV7 STs showed a reduction in the NS rates for penicillin G (PEN; from 30.3% in 2009 to 16.0% in 2015) and ceftriaxone (CRO; from 27.3% to 12.0%), as did PCV13 STs (from 34.5% to 16.0%% and from 27.5% to 8.6%, respectively). ST 19F showed stable S patterns over time and 19A remained the less S ST with high NS rates for PEN (49.0%–76.5%), CRO (24.5–64.8%), erythromycin (ERY; 76.9–90.8%), and clindamycin (CLI; 51.0–73.1%). These NS rates for 19A rose from 2009 to 2011–2012, decreasing in 2013–2016. NS rates for CLI and ERY against ST 3 increased to 19.6% and 23.9% in 2015, respectively. Non-vaccine STs showed stable NS rates for PEN, CRO, and CLI. However, an increasing trend for ERY NS (from 35.2% in 2009 to 45.0% in 2015) was noted, which was driven by increasing NS rates for 35B (from 42.3% in 2009 to 71.2% in 2015). CONCLUSION: PCV13 ST exhibited decreasing trends for NS during the study period, except for ST 3, which showed stable S rates over time. Overall, implementation of PCV13 decreased considerably the NS rates in S. pneumoniae causing infections in the US adult population. Further surveillance will enhance understanding of future antimicrobial patterns in S pneumoniae in the context of adult pneumococcal vaccination programs. DISCLOSURES: R. E. Mendes, Pfizer, Inc.: Research Contractor, Research grant; H. L. Sings, Pfizer, Inc.: Employee, Salary; J. A. Suaya, Pfizer, Inc.: Employee, Salary; L. N. Woosley, Pfizer, Inc.: Research Contractor, Research grant; R. K. Flamm, Pfizer, Inc.: Research Contractor, Research grant; R. E. Isturiz, Pfizer, Inc.: Employee, Salary